“ReferenceError: Cannot access ‘XXXX‘ before initialization“ found in

一、报错截图

报错信息格式：

[Vue warn]: Error in v-on handler: "ReferenceError: Cannot access 'XXXX' before initialization"
found in

---> <BarChart> at src/views/smart-edu/comprehensive-review/components/barChart.vue
       <ElCard> at packages/card/src/main.vue
         <StudentRecord> at src/views/smart-edu/comprehensive-review/index.vue
           <AppMain> at src/layout/components/AppMain.vue
             <Layout> at src/layout/index.vue
               <App> at src/App.vue
                 <Root>
vue.runtime.esm.js?2b0e:3049 ReferenceError: Cannot access 'XXXX' before initialization
    at VueComponent.clickBar (index.vue?6ced:89:1)
    at invokeWithErrorHandling (vue.runtime.esm.js?2b0e:3017:1)
    at VueComponent.invoker (vue.runtime.esm.js?2b0e:1815:1)
    at invokeWithErrorHandling (vue.runtime.esm.js?2b0e:3017:1)
    at Vue.$emit (vue.runtime.esm.js?2b0e:3716:1)
    at VueComponent.handleEvent (barChart.vue?641b:112:1)
    at invokeWithErrorHandling (vue.runtime.esm.js?2b0e:3017:1)
    at VueComponent.invoker (vue.runtime.esm.js?2b0e:1815:1)
    at invokeWithErrorHandling (vue.runtime.esm.js?2b0e:3017:1)
    at Vue.$emit (vue.runtime.esm.js?2b0e:3716:1)

二、报错原因

变量先使用，后定义就会出这个错

三、解决

根据报错信息定位到具体的Vue文件，具体到某个变量，确保其是先定义后使用即可